When the weather is hotter and drier, fires are more likely to ensue. Makes sense – and with climate change now taken as fact rather than scientific scaremongering, it's only logical that global warming is causing more wildfires. And now the math is in.

Scientists don't like to be pushed to the wall and say that a specific conflagration was caused by global warming, let alone by man-made climate change. But as smoke spreads across the skies of California, the trend is clear. Even the governor of California says it straight: California is on the front line of climate change, Jerry Brown told ABC, predicting that 2014 would be the worst year yet for fires.

The governor could be onto something. Looking at the U.S., since 1984, the area scorched by the largest wildfires - those spreading across more than 1,000 acres - have increased by 87,700 acres a year, according to a study in the journal Geophysical Research Letters, published in April. The biggest increase in fires has been where drought has been worsening, a signal that climate change is involved.

The five years with the most acres burned have all happened in the last decade, according to federal records.

In the 1980s, an average of 2.9 million acres burned each year in the U.S. From 2010-2013, that figure had more than doubled, to 6.4 million acres a year.

Piggyback arsonists on longer summers

The wildfires devastating large swatches of southern California may have been caused in part by arson – the first such arrest was made this week, of San Diego resident Alberto Serrato, 57. But even in that case, the police don't think he started the fire, just added fuel to the flames. Which, as they enter their second week, provide a grim vision into the future of drier, hotter lands.

In the past three months, at least three different studies and reports have warned that wildfires are getting bigger, that man-made climate change is to blame, and it's only going to get worse with more fires starting earlier in the year.

Never mind that cooling weather has helped firefighters tame the flames in San Diego: the brief respite from the rising heat was just that – a respite, and a brief one as summer gears up. Meanwhile, as many as 125,000 people had fled their homes in and in the area of San Diego alone.

"The fires in California and here in Arizona are a clear example of what happens as the Earth warms, particularly as the West warms, and the warming caused by humans is making fire season longer and longer with each decade," said University of Arizona geoscientist Jonathan Overpeck. "It's certainly an example of what we'll see more of in the future."

"We are going to see increased fire activity all across the West as the climate warms," Dennison said.

That was one of a dozen "key messages" in the 841-page National Climate Assessment released by the federal government earlier this month. It mentioned wildfires 200 times.

Often the cause of the fires is as man-made as climate change seems to be. The first of the San Diego area fires, which destroyed at least eight houses, an 18-unit apartment complex and two businesses, apparently started from sparks from faulty construction equipment, said California Department of Forestry and Fire Protection spokeswoman Lynne Tolmachoff. And then there's the sheer ill-will of arsonists.

And lightning. Granted California has been periodically stricken by drought, which among its serious costs, can cause a buildup of intensely flammable plant matter – brush and trees alike. All you need is a protracted drought in hot weather followed by a lightning strike and some wind, and you have a recipe for disaster.

Meanwhile, this year California and Arizona suffered their hottest first four months of the year on record, according to National Weather Service records. Parts of Southern California broke records Thursday, racing past 100 degrees. For the past two weeks the entire state of California has been in a severe or worse drought, up from 46 percent a year ago, according to the U.S. drought monitor.

Even the drought has been linked to man-made climate change, in a study also published in Geophysical Research Letters. Not everybody concurs.

Being hot and dry, in general, Israel is also subject to wildfires. The worst one in terms of loss of life happened in 2010, but it wasn't caused by climate change or even arson. It was, police later decided, caused by one or more teenagers ineptly smoking a nargila.

But climate change could be implicated in the results of their mishap. The virtual disappearance of the relatively wet winter season left the Mt. Carmel forest just north of Haifa extremely dry, and when the fire caught the brush, it rapidly spread across the mountain. It claimed 44 lives, most of whom were Prison Service cadets being bused to help evacuate inmates from a prison in danger of catching fire itself.

After several days, during which people were evacuated from villages along the Carmel ridge and from nearby neighborhoods in Haifa itself, the fire was extinguished with the help of fire-fighting planes sent from neighboring countries, including Greece, Turkey, the United States and Russia, the latter fresh from fighting vast wildfires threatening Moscow.

Today vegetation is growing back onto the blackened slopes of the Carmel, but the main attraction there is no longer the forest, but the memorial to the people who died in the blaze.

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